2013's Man of Steel was a lot of fun, but it was far from flawless. The most frustrating part was the ending. But that's one part that has an easy fix. Here's how I'd do it:
More important than Superman's superpowers are his ethics and ideals. Specifically, there's one thing he never does: KILL. And there's one thing he does at all costs: SAVE LIVES. What happens when they conflict? Man of Steel tried to answer that, but it didn't have the weight it needed.
When the final fight with Zod started we should've seen a reluctant Superman- one who knew that this fight was to the death. Once the collateral damage begins, with people dying and property being demolished, Zod should notice the concern from Superman and adopt his "I'm gonna destroy this planet you love so much" strategy.
Zod begins throwing cars in the air, mowing down hordes of people with laser vision, whatever he can do to hurt the petty eathlings. All the while, the man of steel is doing everything he can to save the people -- catching cars and people falling from skyscrapers, throwing himself in front of Zod's laser vision, etc. At one point, Zod brings down a building that Supes catches and struggles to keep it from crashing to the ground. Zod takes the opportunity to use Kal-El as a Kryptonian punching bag.
No matter how many people Superman saves he can't save everyone. Zod is mowing down hundreds, and Clark is taking a beating because he can't defend himself from Zod's attacks while trying to defend the people. Clark's anger begins to well up, and he finally unleashes an onslaught upon Zod.
Meanwhile, Perry White and Jenny Olsen are working hard to evacuate people from this alien battlefield (Sidenote: in this iteration Metropolis has a bridge similar to the Golden Gate Bridge that leads off the island when the brawl is occuring). Most people believe they'll be safer across the bridge, so there's a mass exodus away from the carnage.
Zod and Kal-El's battle becomes more vicious and brutal as Supes' anger worsens. Zod smashes cars on top of Clark, Clark beats Zod into the pavement, etc. (Just actions scenes I personally wish I could've seen). The two Kryptonians become exhausted and battered (Zod's armor should be falling apart and Superman's suit should be ripped- another little touch we missed out on in Man Of Steel).
*Things get a little complicated here, so buckle up*
At this point, Zod should notice that there are thousands of people crossing the bridge. He destroys the beams on one side and prepares to do the same to the other side, which would send thousands of people crashing into the water. Superman sees what Zod intends and attempts to force him away. Then Zod decides to use his laser vision to disconnect the remaining side of the bridge. Superman desperately tries to pull him away, but Zod is determined. He even tries to fly away, but Zod's feet are firmly in the ground. Clark begs him to stop. Zod finally gets to make his "If you love these people you'll watch them suffer!" line.
So Superman has to make the decision. He has to kill Zod (yes, he snaps his neck) to save thousands of people (not 4 people). Clark then collapses from pain and exhaustion while the people of Metropolis watch. Lois rushes to his side. Next thing we see he wakes up at a government base and is able to have his conversation with the general where he basically tells Superman, "Thanks, but we still don't trust you." And Superman says he's here to stay. Lois writes a propaganda article entitled "Man of Steel" explaining how Superman saved the world due to the polarizing opinions about his presence on Earth. Perry okays the article reluctantly even though he doesn't trust Superman either.
*Reasons for my changed ending:
-I added the stuff with Zod killing people and Superman saving people during their battle because that's what Superman would ACTUALLY shows how much he really loves the people of Earth and that his loyalty lies here.
-I added the other little touches (reluctance, brutality, anger, additional action) to the fight because it needed a bigger payoff and more weight to the whole battle.
-I added the bridge sequence because Superman's decision to kill Zod needed more weight and emotion it. He had already killed a lot of people, and thousands more were about to die (not 4 people... THOUSANDS). Everyone in the theater would know that he had no choice. He HAD to kill him.
-I added Lois Lane's article because there needed to be more reason behind the movie's awesome MAN OF STEEL title (if you don't have good script writers, this article could go into cheesy territory. But it could be a strong ending if written well). This was also added so we would know that some people were accepting of Superman while others were terrified and angry, setting the universe up for whatever controversy is surely planned for the sequel. Public opinion is NOT something the actual movie covered.
Big finish: when he was driving back to Smallville to see his mom (it's important that he's driving instead of flying because that's what eathlings do) "Earth" -- Hans Zimmer's track from the movie's score that was NOT used in the actual movie -- plays in the background. The fantastic music and some beautiful scenery shots of the Kansas landscape would drive home the fact that Clark has chosen to be a citizen of earth, and he is permanently home here among the humans. He's an eathling in his heart and he always will be. That's the main theme of Superman's story, anyway. And though I like this movie, I feel like these scenes would convey that theme better.